How to Manage Pests
UC Pest Management Guidelines
Leaffooted Plant Bug
Leaffooted plant bugs are a frequent and highly damaging pest of pomegranate. Adult leaffooted plant bugs are large insects, 0.75 to 1 inch (19–25 mm) in length. The three leaffooted bug species are similar in appearance; they are brown in color with a narrow white zigzag band across the back, although this band is less distinct in L. occidentalis and L. zonatus has a round yellow-orange patch on each shoulder. The head appears pointed and the hind legs have an expanded area that superficially resembles a leaf, hence its name.
Leaffooted plant bugs overwinter as adults, typically in large groups in citrus orchards, or in protected areas, such as in woodpiles, barns, and under the bark of eucalyptus, cypress, or juniper trees. In pomegranate, leaffooted bugs feed on the fruit in the fall and may remain in the orchard through the winter. Pomegranate orchards with cracked fruit left on the trees are a favored overwintering site where they may cluster in plant debris, pump houses, or cracks along the tree trunk.
Spring numbers are determined by the population the previous fall and by wintertime temperatures. Cold winters kill many overwintering adults. Outbreaks typically occur after several years of moderate winters, which allow numbers to increase.
These insects are primarily seed feeders and, once in the orchard, they will feed on the developing fruit or ground vegetation seeds. Adults are strong flyers and can quickly move into and within the orchard. In the spring, they can be found in the orchard and also migrating out of the orchard to nut crops such as almond and pistachio (April and May). During the fall, leaffooted plant bugs also migrate to citrus.
Overwintering adults live from September to May. Eggs are laid in spring, usually on leaves and twigs; adults deposit eggs (some over 200 eggs) that look like brown strands of beads. After nymphs emerge, they develop into adults in 6 to 8 weeks. Because the adults are long lived and can lay eggs over an extended period, the population can consist of all life stages by late June. There may be 2 to 3 generations per year, depending on temperature and food sources.
Leaffooted plant bugs can build up in very large numbers in pomegranate orchards, with more than 100 nymphs on a single piece of fruit. Feeding damage is not easy to see on the outside of the fruit. The bugs pierce the thick skin of the fruit to feed on the arils, causing them to wither. Bugs prefer to feed on fruit already split. Although leaffooted plant bugs are found in various crops throughout the year, high numbers and damage occurs only late in the season when they return to pomegranate just prior to harvest.
Many feeding bugs on a fruit deposit feces, which may increase the incidence of disease. Occasionally rot is found inside feeding wounds, but it is not certain whether the insect introduces the pathogen during feeding or if the pathogen enters later through the feeding wound.
An occasional adult leaffooted plant bug on fruit is tolerable, but numbers should not be allowed to build. Remove all fruit before winter to decrease the number of overwintering bugs. Native egg parasites, such as Gryon pennsylvanicum, if not disrupted, also help keep numbers down. Outbreaks, especially in late summer or fall before harvest, should be treated quickly, before serious damage can occur.
The egg parasite, Gryon pennsylvanicum, provides partial to good control of leaffooted plant bugs, especially if host numbers are high. Eggs with round exit holes indicate presence of the parasite.
Remove all fruit before winter to greatly reduce the number of leaffooted plant bugs overwintering in an orchard. Cleaning debris from near the orchard may also help. Cold temperatures near 23°F (5°C) will kill most exposed bugs, while those protected from winter weather survive better. If possible, remove other nearby overwintering hosts such as juniper.
Where possible, manage leaffooted plant bugs in neighboring crops to prevent migration into pomegranate. Use cultural controls to reduce overwintering numbers. Pyrethrin may kill some nymphs but control efficacy is variable.
Leaffooted plant bug outbreaks occur areawide so if problems are observed in almonds or pistachios, also look for them in pomegranates. Be wary after mild winters, or if high numbers were found the previous fall. Scout orchards for individual adults or masses of nymphs on fruit during September and October. Higher numbers will be found closer to harvest.
Treat as soon as adults are observed to prevent egg laying and nymphs, which are difficult to control since they hide under tree bark. Methomyl (Lannate) is the most effective insecticide, but can disrupt natural enemies important for the control of other pests.
|Common name||Amount per acre||R.E.I.‡||P.H.I.‡|
|(example trade name)||(hours)||(days)|
|The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.|
|(Lannate SP)||1 lb||48||14|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Disruptive to natural enemies of mealybugs, caterpillars, soft scales, aphids, and other pests. Use of this material may result in outbreaks of these pests.|
|(PyGanic EC 1.4#)||2–4 pts||12||0|
|MODE-OF-ACTION GROUP NUMBER: 3|
|‡||Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I. The longer of two intervals is the minimum time that must elapse before harvest.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.|
|#||Acceptable for use on organically grown produce.|
UC IPM Pest Management Guidelines:
UC ANR Publication 3474